This project is concerned with the problem of regulatory phenomena during development as exemplified by biochemical aspects of cellular proliferation and differentiation. The functional unit of the intestine comprised of the crypt and the villus has been a focus of these studies. In the crypt and other model cellular systems, de novo pyrimidine biosynthesis is being studied in relation to proliferative growth. In the intestinal villus, the dissaccharidases and absorptive transport functions are being used as markers of differentiation with genetic and environmental factors (e.g. diet) being examined in particular. Study of intestinal developmental disorders is included as a part of this research project.